Motor mount and motor drive means for phonographs



Nmr. 3Q, E@4. v, SWEIGHERT f?- MOTOR MOUNT AND MOTOR DRIVE MEANS FOR PHONOGRAPHS Filed Jan. 5, 1945 I N VENT OR. 04MB M uxvi/a/yrer F76. 3 BY was long ago proposed to ing elements of motor shaft roller and the said idler wheel enatented out p casters MQ'EOR MOUNT AND MOTOR DRIVE ANS FGR PHDNOGEAPHS David V. Sweighert,

The General industries Company,

a corporation or @hio Cleveland, Ohio, assignor to Elyria, Ohio,

application January 5, 1945, Serial No. srmis My invention relates to improved motor mount and motor drive means for phonographs.

For the driving of phonograph turntables, it

efiect such driving by frictional contact of a driving roller with the interior surface of a peripherally disposed pendant turntable flange, and more recently, an intermediate idler wheel has been interposed between such flange surface and a driving roller directly positioned on an upwardly'disposed end or the driving motor shaft, said idler wheel being supported by a mounting plate underlying said turntable and adapted toeflect resiliently applied frictional engagement between the usual rubber tread of such idler wheel and the relatively, hard enga ing portions of said turntable flange and driving roller, the motor carried by said supporting plate.

In some cases, the support for said motor has been in the form of a plurality of rubber grommets or the like with mechanically rigid connections, each with the periphery and central portions oi said grommets whereby said grommets are rigidly nections between said plate and said motor whereby motor noise may not be transmitted through the motor shaft driving roller and idler wheel to the turntable and thence to a turntable supported record, and ultimately to the-sound pickup device of the phonograph.

The interposition of such rubber motor mountwhich three or four are common- 1y provided has resultedin. the practical elimination of motor noise to the phonograph pick-- up, but still objectionable character have been introduced as a resultoi the motor cushion mounts,

towit:

Since the motor is not rigidly secured to the base plate, it tends to vibrate, such motor vibrations being-sometimes caused by bodil movement imparted to the entire phonograph casing by vibrational movements of its underlying floor, or other support, and again from the rotational movement of the motor rotor commonly augmented by variable friction edects between the gaged thereby. V

In any event,l find that such motor movements communicated to the driving roller create variable friction eflects as between said roller and said idler and thereby sets up a pulsation of speed variations in the and supported record whereby the sound reproduced from the record by the action of the pickup being usually p endantly interposed in motor supporting conbut I- find that tonal defects of a difierent 1 215 (ll. (clam-c) are not reproduced with such fidelity as to satisfy the more critical music lovers.

In analysing the problem thus presented, I have found that the vibrational effects tend to create a swinging of the pendant motor in variable' patterns but the more noticeable deleterious eflects are caused by vibrational movements of the motor tending-to effect corresponding move-' 1 merits of the driving roller about an axis which is relatively spaced from the point of engagement between the roller and idler wheel and such more objectionable movements being such as to tend to separate the roller and idler wheel, and alternatively to increase the pressure of contact therebetween.

. These vibrations sometimes achieve a periodicity which approximates the periodicity of the en-- tire interlinked parts'comprising-the motor, the

rubber mounts and the rubber tread for the idler at which times the distortion of the reproduced sound is readily noticeable.

My invention therefore relates to an improved position of the rubber grommet motor mounts with respect to the engaged surfaces of the driving roller and the idler wheel tread whereby the axis of any such vibratory efiects passes either exactly medially between the engaged surfaces of driving roller and idler tread that swinging movements of the motor about such ams will produce the minimum variation of driving effect as between said motor roller and said idler wheel and consequently, to minimize any such sound distorting effects proceeding therefrom through said turntable flange to the rotating turntable supported record.

An object of any invention therefore is to mini- I mize the sound distorting eflects of a vibrating rotation oi the turntable cushion mounted motor in a friction drive mechanism for phonographturntables. Another object of my invention is to improve the tonal qualities of phonograph record reproductions from a phonograph mechanism with a motor driven friction drive transmission for r0- tating the turntable.

Another object of my invention is to provide improved means and method for pendantly supporting the electric motor, as commonly employed in friction drives for phonograph turntables, whereby oscillatory movements, of the motor on the shaft of which a driving roller is aiiixed, are so constrained as to have the center of such oscillation located in the horizontal plane of the contacting engaged motion-communicating sur faces of said driving roller and the rotatable element through which said roller is adapted to frictionally drive the turntable.

A more specific object of my invention is to achieve the foregoing object in a manner whereby such center of oscillation is also disposed at or, at least, close to the zone of said engagement.

Another object of my invention is to achieve approximate positioning of the said center of oscillation suflicientlyclose to said zone of engagement to ensure that such movements will not appreciably be reflected in resultant periodic variations in driving torque as between said roller and the driven element of said motor and turntable drive.

Another object of my invention is to achieve any or all of the foregoing objects in a more complete manner by providing the said engaged surfaces with such a form that, notwithstanding a substantially minor spacing between the said center of motor oscillation and the said zone of friction driving contact, oscillatory bodily movement of said motor will not result in appreciable variations in driving torque between the said motor roller and the driven element of said drive mechanism.

. Other objects of my invention and the invention itself will become more readily apparent from a purview of the accompanying drawings and description thereof which follows.

In the drawings:

Fig. 1 is a partial plan view showing a turntable drive embodying my invention with a portion of the underlying turntable and certain of the underlying parts broken away .to expose certain underlying parts;

Fig. 2 is a sectional elevation taken through the device approximately as indicated by line 2-2 of Fig. 1; and

Fig. 3 is a sectional elevation taken through the device of Fig. 1 approximately as indicated by line 3-3 of Fig. 1.

The drawings illustrate a single preferred embodiment of my invention, as shown in Figs.

1 to 3 inclusive, my improved turntable driving device comprising, in general, a rotary turntable I, rotatably mounted on a turntable spindle 2, said turntable comprising a downwardly extending peripheral flange or rim portion 3 with which an idler wheel 4 is adapted to have frictional engagement by means of a rubber tire or friction tread 5 which is fitted peripherally about the idler wheel 4.

4 I turntable flange 3 whereby the rubber treadof said idler wheel contacts the peripheral surface of the roller I 6 and the intra-peripheral surfacev of the turntable flange 3 at portions of its tread surface angularly separated an amount approximately midway between 90 and 180. The idler spindle and the contact between the idler tread and the turntable flange thereby defines an obtuse angle.

The above relationship between the roller, the idler and the turntable is a preferred arrangement'previously known.

The motor A is pendantly supported by the mounting plate 9 by posts 13 and i4 vertically secured to the motor casing and extending parallel to the motor shaft 34 which projects through an enlarged aperture 35 of the mounting plate 9, and carrie'sthe driving roller 15 at its upper end. The motor supporting posts l3 and M are secured to upstanding tubular posts I 9 and 20 through the instrumentality of the rubber grommets l1 and I8, which grommets are fitted over the expanded upper flange portion 2! of the posts, the grommets being normally molded to such smaller size as to require stretching in order to snap the peripheral flanges of the grommets over the posts i9 and 20.

The upper end of the motor supporting posts I3 and M are preferably threaded, as shown, and a pair of nuts 22 and 23 threaded onto said posts above and below the medially apertured portion of the grommets to clamp the upper ends of the motor posts to the central portions of the cushioning grommets. The tubular grommet supports l9 and 20 are preferably headed over at their slightly reduced lower ends, as shown at 24, after projection of such reduced lower ends through circular apertures of said mounting plate 9.

The idler wheel'is mounted to revolve about a spindle 6 which is carried by an enlarged end I of a sliding arm 8, 'said sliding arm being, in turn, mounted upon a mounting plate 9. The means for securing the arm 8 to the mounting plate 9 comprises a screw [0 and a washer I2, also a tongue l5 of the mounting plate 9 projected upwardly through an elongated slot 44 at the end of the arm, which is remote from the spindle 6,'said screw being threaded into the plate 9 and said washer being but loosely confined between ,the head of the screw l0 and the upper side of the arm 8.

The screw III is projected through an enlarged opening ll of the arm 8 and its lower end is threaded into the plate 9 sufliciently to loosely retain the washer l2 in place and similarly, the tongue [5 but loosely projects within the elongated slot 44 of said arm. 4

The idler wheel is therefore adapted to freely float under the resilient influence of the tensile spring S to a driving'position between the motor driving roller is and the inner surface oi the I consider it important to position the points and connection, indicated at 42, Fig. 2, in the horizontal plane which contains the zone of engagement between the motor roller l6. and theperipheral surface of. the idler wheel tread 5, and where, as preferred, the outer tread surface is rounded, as illustrated, said plane shall preferably include the peripheral portion of said tread which is of greatest diameter. In Figs. 2 and 3, the above recited plane is indicated by the broken line 40-40.

In the present embodiment, only two motor supporting posts [3 and H are provided whereby vibratile or other oscillations of the motor A will be on an axis corresponding with the line 25, indicated in Fig. l, and whereby the pressure contact between the motor roller I6 and the idler wheel tread 5 will be neither increased nor decreased during any such oscillatory movements, and during such movements, the motor oscillations will be about a center, shown at 4|, Figs. 1

and 2, there being only an exceedingly slightv roiling movement of the engaging surface of the roller IS on the preferably curved peripheral surface of the idler tread 5. There will not be an appreciable variation in the power transmitted from said motor roller to the idler wheel.

Although more than two grommet supported motor posts may be provided in other embodiments of my invention, such as two additional such posts, if these are placed symmetrically with respect to the placement of the two posts 13 and I 4, and the point of medial contact as between the roller is and the contacted idler wheel periphery, the same avoidance of appreciable aeeeaeo the grommet centers and, indeed, there may be other oscillatory movements in directions which are the result of movements in the above related right angularly intersecting planes; however, in every case, the center of any suchsimple or compound oscillatory movements will be located according to the placement of the grommets at or.

close to, the intersection of the horizontal plane ddld and a line such as the line 2b.

In effect, the motor, representing most of the weight or the oscillatory system pendulously supported by the plurality of flexible grommets d2, oscillates about a center which, in the embodiment illustrated, is located at the point ti and the oscillatory system partahes of the nature of .a pendulum, the length thereof extending from such center of oscillation to the center of mass which is located at some such point as is indicated by X," Fig. 2.

The oscillatory moveme t of any part of said system, such as at the point X," is such a dractional portion of the movement at m, accordof such'oscillatory oentenas provided in the illustrated embodiment, is ideal.

.I aware that my invention is susceptible to variations in the positioning of such center and that it is not always possible to fully achieve the most desirable positioning herein illustrated in l o structures manufactured in quantity production but, fortunately, within the above range of permissible variations, I find that the results are considerably superior to that formerly obtained and I thererore claim as my invention the combination or elements positioned as set for-thin the following claims both broadly as ineluding such permissible range of variations, and" more specifically, in certain of said claims wherein said ideal positioning of the center of mode of oscillation is more closely and/or precisely I claim:

1. In a phonograph turntable drive of the type described wherein the saidv turntable is frictionally driven by the engagement of the peripheral tread oi the idler wheel with a pendant flange oi the turntable, and wherein said idler wheel at another polnt in its circumference is peripherally 'frlctionally engaged by the periphery of a motor driven driving roller of such substantially lesser diameter .than said idler wheel thatsald roller may be driven at a relatively high speed to effect frictional driving by said idler wheel of the turntable at a reduced rotational speed, the combination with a motor having an upwardly projectin ing to the relative distance oi. the point x? and the point X" from the center of oscillation indicated at M, Figs. 1 and 2.

While I prefer to so position any desired practical plurality of flexible supporting grommets,

'such as H and it, with respect to the center of mass of the oscillatory system, roughly indicated at X," the center of oscillation will be precisely loca at the precise center of the area of interengag ment of the peripheral surfaces of the roller t and the idler wheel tread 5 and advantageous results may be obtained so long as said center of oscillation is not spaced from said central point of said area of interengagement ti more than one-fifth of the efiective length of the oscillatory system, considered as a pendulum.

I prefer however to make such relative distance not more than one-half of the above value, or one-tenth of said distance, and as above stated, this may be accomplished by using 2, 3, 4 or more flexible elements, such as the grommets ill, for supporting the motor whose center of mass is roughly indicated at X.

As an added feature of improvement, I may add weighting means, such as the weight W,'' to the oscillatory system at any suitable point to oflset the otherwise greater weight of the motor or any other part of the oscillatory system comprising such motor, and which may be efiective at the opposite side of the motor whereby the motor will hang pendantly, without including the posts it and it nor the motor shaft M, from the, vertical. Usually, however, the posts such as it and It, and others if more than two grommets are employed, may be so distributed laterally with respect to the upper surface of the motor so that the stated purpose of said weight may be efiected without utilization of any such weight.

Within the above range-of permissible variations oi placement of the center of oscillation, I find accomplishes substantially better results than have heretofore been accomplished in prior constructions and the precise positioning shaft, said pendant flange, and said idler wheel. a roller carried by the upper end portion of said motor shaft, and means affording a common support adapted to maintain said roller flange and idler wheel, in substantially the same horizontal plane; means for resiliently 'and'yieldab'ly urging said idler wheel into predeten'nined pressure contact with both said roller and said turntable flange, and a plurality of supporting elements for pendantly supporting said motor from said support, said elements comprising substantially rigid means extending upwardly from said motor into 4 said plane, substantially resilient cushioning means interconnecting said support and said rigid means, said cushioning means being so disposed as to afiord a horizontal extending pivotal swin ing axis for said shaft supported roller, with said swinging axis passing substantially tangentially through the inter-engaged portions of the idler wheel periphery and the roller periphery.

2. In a phonograph drive mechanism of the type described, the combination with a phono-.

graph turntable having a pendant flange, a motor, a shaft therefor, an idler wheel, and a common support for said turntable, motor and wheel, said shaft extending upwardly and its upper end adapted to afiord a driving roller peripherally engaged with said idler wheel, said idler wheel being peripherally engaged with the inner surface of said flange, mounting means interconnecting said motor and said supportcomprising at least a pair of flexible elements. both carried by said support in interspaced relationship, and said elements having flexible portions disposed sub-- stantially both in the horizontal plane of interengagement of said roller and wheel, and in the vertical plane thereof which is tangential to the roller engaged portion of the wheel periphery to afford a horizontal swinging axis for said roller, said axis passing tangentially through the engaged wheel and roller surfaces.

3. Mounting means for yieldably pendantly supporting the driving motor of a phonograph drive mechanism of the type described, the combination with the idler wheel, and driving roller thereof and a fixed support, said roller axially secured to the upwardly extending end of the motor shaft, said wheel and roller being operatively peripherally interengaged for driving of said wheel by said roller, and mounting means comprising at least a pair of flexible elements both carried on a fixed support and both disposed in a vertical plane which is parallel to and so closely adjacent to the vertical plane of the interengaged peripheral surface portions of said roller and said wheel, and also so closely adjacent to the horizontal plane of said interengaged surface portions, and said elements being so nearly similarly laterally spaced from said interengaged surface portions, as to cause said flexible elements to afford a horizontal swinging axis about which said roller can only be moved, whereby swinging of said motor and roller as a unit such as normally encountered in the operation of the device may be had without impairment of normal operating pressure engagement between said roller and said idler wheel periphery.

4. In a phonograph drive mechanism of the type described comprising a disc-type turntable, the combination of a motor having an upwardly projecting shaft, 9. pendant flange for said turntable, an idler wheel, and a roller carried by an upper end portion of said shaft, and means affording a common support adapted to maintain said roller, flange and idler wheel in substantially the same horizontal plane, said wheel and roller being operatively peripherally interengaged for driving said wheel by said roller, and mounting means comprising a plurality of flexible diaphragm elements, means securing a portion of each of said diaphragm elements to said fixed support, and rigid means joining said motor to another portion of each of said flexible elements whereby the motor is yieldably pendantly supported by said elements, all said elements being relatively so disposed in the line which is tangential to the interengaged peripheries of said wheel and roller, and at the level of such interengagement as to constrain pendulum-like oscillations of said motor to oscillatory movements about an axis in the region of said interengagetangentially to the engaged peripheral portions of said wheel and roller whereby oscillatory movement of the roller about said axis will be limited to vertical movements and said system having a roller adapted during such movements to maintain substantially uniform engagement between the driving roller and idler wheel periphery.

DAVID V. SWEIGHERT.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,234,811 Shelton July 31, 1917 2,097,071 Lichten Oct. 26, 1937 2,161,148 Erwood June 6, 1939 2,262,731 Gurber et al. Nov. 11, 1941 2,386,503 Pressley Oct. 9, 1945 

